GOE rims ordered: Now I need to sort out tyres.

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Originally Posted by Tombie

Partially it is stones thrown back at the rear tyres, and the stones turned up by the front tyres passing over then being run over by the rears.

This should also be evident on the trailer tyres though.

The other, and most primary cause is tyre pressures...

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We were running 36psi in the rear and a bit less in the front. I don't go lower when doing thousands of km at relatively high speeds on gravel roads with heavy loads.


It is definitely the stones getting turned over and flung up by the front tyres. In fact, I think the rears get peppered directly with rocks coming from the front wheels. The trailer tyres also show some similar damage but nowhere near as bad. The trailer itself is another matter, even with a Stone Stomper guard.


The D697's have a large gap between the treads which I think allows sharp rock to inflict a bit of damage to the casing. On BFG tyres that I have seen the tread is always badly damaged by rocks but the casing is fine.


The only thing that worries me a bit is that the casing between the treads is cracked near each tread block, like a perished tyre. It looks like the tread is putting local stresses on the casing and causing it to crack. This is what the tyre fitters were worried about. This suggests to me that perhaps the tyres are under inflated for the loads I am putting on them but as per other posts, you also don't want the pressures too high for rough and rocky roads.


I found after our trip to Cape York last year using Continental Cross Contacts on GOE rims that the rear tyres took a real pounding also and were nearly worn out after the trip, with quite bad tread damage due to rocks etc as well.


Bob

I would suggest at 36psi you were overinflated for those loads... By a long Margin!

Fully laden, and on a week long trip running at speeds up to and including 120km/h running at 24psi...

No damage to the tyres...

Your pressures are causing the damage as the tyres can't flex over the stones...

Contact Bridgestone and send some pics, but I'm confident it was the pressure you ran doing the damage.

Quote:

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Originally Posted by Tombie

Fully laden, and on a week long trip running at speeds up to and including 120km/h running at 24psi...

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Interesting, would have thought that a bit low.

24psi all round? Is that hot?
120km/h on gravel or bitumen? For long periods or just short bursts?

How much do the sidewalls bulge on those tyres at that pressure?

Genuine questions, not trying to start an argument.

Cheers,
Jon

Yeah, I don't believe in high loads at high speeds at such low pressures. I would rather damage the tread than wreck the side walls and get a blow out.

My two rear Continentals have been destroyed six months after the Cape York trip, one of them with a major side wall faliure on bitumen in Perth at 100kph and at LR specified tyre pressures. This was after we did much of the trip at 28psi on rough roads at fairly high speeds and maximum GVM. After this I decided not to lower tyre pressures at high speeds on rough roads as a precaution. I should add, though, that the Continental tyres have side walls not much thicker than cardboard, unlike the D697's.

We were travelling to Cape York with Cruisers and I wanted to travel at 80 with lowered tyre pressures but they took off and left me behind and I ended up having to drive fast on low pressures to catch them.

Bob

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Originally Posted by BobD

Yeah, I don't believe in high loads at high speeds at such low pressures. I would rather damage the tread than wreck the side walls and get a blow out.

My two rear Continentals have been destroyed six months after the Cape York trip, one of them with a major side wall faliure on bitumen in Perth at 100kph and at LR specified tyre pressures. This was after we did much of the trip at 28psi on rough roads at fairly high speeds and maximum GVM. After this I decided not to lower tyre pressures at high speeds on rough roads as a precaution. I should add, though, that the Contental tyres have side walls not much thicker than cardboard, unlike the D697's.

We were travelling to Cape York with Cruisers and I wanted to travel at 80 with lowered tyre pressures but they took off and left me behind and I ended up having to drive fast on low pressures to catch them.

Bob

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I'm not surprised, Continentals are rubbish and not LT.

Loaded with a trailer I run 44psi on the tar, if I'm going to be on the gravel for long periods I drop them to 30psi and usually cruise around 80 odd KPH, 24psi is too low at the speeds Tombie mentioned in my opinion, especially on the tar, but OK if doing say 80 to 90KPH.

Baz.

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Originally Posted by jon3950

Interesting, would have thought that a bit low.

24psi all round? Is that hot?
120km/h on gravel or bitumen? For long periods or just short bursts?

How much do the sidewalls bulge on those tyres at that pressure?

Genuine questions, not trying to start an argument.

Cheers,
Jon

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The 24psi was cold inflation pressure at 8am on a warm day.

120km/h was on the loose surface, chasing up to the group and was sustained usually for bursts of 20 minutes each hour - I rang a forum member during this time and was having a laugh (3G coverage along the rail corridor).

Average speeds were between 80-90km/h and the vehicle had no issues at those speeds on those pressures.

The sidewalls have a mild flex at those pressures but nothing of concern.

There was never any doubt about the tyres at this pressure - the higher the pressure, the more likely to be pierced by a rock rather than conform to it and move on.

Hard tyres and rocky surfaces don't mix - and usually I would recommend pressures down and no faster than 80-90km/h but the D4 makes it easy...

Running high pressures in off-road conditions is inviting damage, as the comments above attest.

I learnt this lesson years ago, destroying the rears on my D1. Since then I've always aired down, and my tyres show no damage, on any of the vehicles.

Quote:

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Originally Posted by BobD

Yeah, I don't believe in high loads at high speeds at such low pressures. I would rather damage the tread than wreck the side walls and get a blow out.

My two rear Continentals have been destroyed six months after the Cape York trip, one of them with a major side wall faliure on bitumen in Perth at 100kph and at LR specified tyre pressures. This was after we did much of the trip at 28psi on rough roads at fairly high speeds and maximum GVM. After this I decided not to lower tyre pressures at high speeds on rough roads as a precaution. I should add, though, that the Continental tyres have side walls not much thicker than cardboard, unlike the D697's.

We were travelling to Cape York with Cruisers and I wanted to travel at 80 with lowered tyre pressures but they took off and left me behind and I ended up having to drive fast on low pressures to catch them.

Bob

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The bruising to a tyre thumped at high pressures can fracture cords just like you have described.

Tread failure - of which I've seen several - can also occur as a 'blow out' scenario due to fracturing of tread and belt surface from stones at speed.

My son had this recently after 'playing' on the rocks at high pressures he hit the highway home and blew a LHF through the tread at 100 clicks - luckily he held it!

As Baz said - **** tyres are **** tyres so the Contis were probably already damaged due to their design shortcomings. Although at 6months after your trip it can't be directly attributed.


Don't forget, tyres are like a balloon.

At high pressure one barely needs to poke a balloon with a pencil to pop it. A half inflated balloon doesn't pop, it deforms around the end of the pencil and resists damage. A flexible strong sidewall, and tread will do the same.

For visual content! These tyres are 40,000km old and over 50% of that is offroad.

Front:
Attachment 69663

Rear:
Attachment 69664

And as a comparison, here's the tyre on the back of our D2 - 65,000km old and used mainly for play on rocks and offroad trips... This vehicle weighs in at 2,800kg without loading it.
Attachment 69665

Tyre pressures *are* important...

Quote:

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Originally Posted by Tombie

The 24psi was cold inflation pressure at 8am on a warm day.

120km/h was on the loose surface, chasing up to the group and was sustained usually for bursts of 20 minutes each hour - I rang a forum member during this time and was having a laugh (3G coverage along the rail corridor).

Average speeds were between 80-90km/h and the vehicle had no issues at those speeds on those pressures.

The sidewalls have a mild flex at those pressures but nothing of concern.

There was never any doubt about the tyres at this pressure - the higher the pressure, the more likely to be pierced by a rock rather than conform to it and move on.

Hard tyres and rocky surfaces don't mix - and usually I would recommend pressures down and no faster than 80-90km/h but the D4 makes it easy...

Running high pressures in off-road conditions is inviting damage, as the comments above attest.

I learnt this lesson years ago, destroying the rears on my D1. Since then I've always aired down, and my tyres show no damage, on any of the vehicles.

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Makes a bit more sense. Any idea what the pressures were hot?

Know what you mean about the D4 making it easy. I must admit I enjoy turning the DSC off on dirt roads and letting it drift.

Certainly agree with what you are saying about about hard tyres and rocky surfaces. Still would have expected that those pressures were a little low, but have no experience of those tyres and not sure exactly of the surface you were running on, so am not in a position to disagree.

Personally, I don't think there's any magic number and just set my pressures by feel.

Cheers,
Jon

After 3 hours at 100km/h on loose surfaces I pulled up on bitumen to air up and pressures were at 26-28psi

The rest of the group were running even lower than I was! Several went down to 22psi on theirs and they were fully laden Cruiser Dual Cabs with Tvans attached.